Answering many of the most critical questions concerning the IV-AIDS epidemic requires long-term data. Accordingly, this proposal seeks funds to conduct a longitudinal study of HIV infection in a non-clinical sample of 614 IVDUs. They were recruited by outreach from the street corners of three small cities during a previous study. Three times during a year, the previous study interviewed the IVDUs in detail regarding sex and needle use, and the subjects were tested each time for HIV. Half the subjects were exposed to a community-wide outreach intervention to prevent the spread of AIDS. Capitalizing on this one- year database and continuing access to the sample, the proposal aims to produce a five-year longitudinal study by conducting four more yearly follow-up interviews and HIV tests. The current staff has achieved a high follow-up rate with these subjects in the last wave of interviews, and the project files have extensive location information on the subjects. The study therefore anticipates completing follow-ups with 90% of the subjects each-year, and will use new analysis techniques to adjust for attrition. The resulting data will be used to assess the long-term effectiveness of AIDS prevention, determine the stability of changes in risk behaviors, describe the sero-conversion rate over time, and prospectively study the tendency of the infection rate to level off. The project will also use a computerized map to analyze the data on residence and HIV status in order to track the epidemic geographically over time, and will examine the impact of AIDS on homeless and non- homeless IVDUs over time.